Monday, August 25, 2014

A Couple of New Woodsman Knives and Some Thoughts on Knife Design: Full Tang vs Stick Tang

A proper woodsman’s knife has three characteristics.  First it must be capable of taking abuse.  By that I mean the knife might be called upon to perform tasks ranging from digging to butchering to building a small shelter.  Second, the blade’s bevel must be strong enough to take light chopping as used for acquiring kindling or other camp craft.  For that reason a Scandinavian grind is not the preferred bevel if the knife is used in regions where hardwoods have specific gravities above 0.75.  Third, the design should promote ergonomic compatibilities associated with prolonged use.  Finger grooves on the handle, for example, might look cool but are a hindrance over time.  A woodsman’s knife is not a lightweight but neither is it a ponderous contraption.  George Washington Sears (Nessmuk) decried the use of bulky knives preferring instead a thin bladed butcher knife.  But Nessmuk carried three blades instead of just one and as such his heavy blade was a small axe.  He also brought a pocketknife on his camping trips.  Mind you, a pocket knife should be part of your always carried items along with a butane lighter, bandana, some cordage and a sharpening device.  But a woodsman’s knife is a generalized tool used for building traps, batoning firewood, constructing wickiups, making a selfbow and marking trees along the trail.  As such the woodsman’s knife is perfect at nothing in particular and yet perfect for all things common.

A woodsman’s knife is made heavier with a full tang but that is the preferred design.  Allow me to make a point: First, not every knife that is claimed to have a full tang has a full tang.  This is perhaps one of the most important bits of information you will come across regarding knife design.  There are stick tangs out there that far surpass the strength of many so-called full tang knives.  This requires some elaboration so please bear with me.  In order to lighten the knife some knife-makers skeletonize or “Swiss Cheese” their full-tang models.  You will purchase a knife thinking it’s a bona fide full tang but if you look beneath the scales you’ll see that in fact your full tang is but a façade.  Now this is the important part: The most stressed area of any knife is just beyond the handle at the end of the blade and immediately to the rear of that section within the handle.  Please refer to the photos below.  If a knife is going to break its most likely spot to crack or split is in the area described above and shown in the photos.  If a knife has been overly skeletonized in the area described then you have a tang that is inferior to the oftentimes belittled stick tang.  And here’s even more bad news: Many of the most popular full tang “survival knives” are overly skeletonized.  In fact, I’ve examined some of the bestselling survival knives and found them wanting.  I won’t mention any brands or makes but armed with this information and you’ll be able to spot the inferior designs yourself.  I am convinced that many knife-makers do not consider the physics involved when designing their knives and this goes for even some of the larger manufacturers.  One popular brand “survival knife” I examined has only two small steel connections beyond the end of the blade.  Between the two connections is a large hole aimed at lightening the overall weight.  Even if properly heat treated and tempered at those two points the knife is still fragile and given the right sort of bump and chop it will break!  A sturdy and sufficiently long stick-tang therefore is preferable to the poorly thought-out “full tang” that’s been given the Swiss cheese treatment.

Note the two small steel pieces posterior to the forward pin hole.  That’s your tang and everything beyond those two points is superfluous when considering stress factors.

The stick tang knife shown in the above drawing is actually stronger than the “full tang” knife above it because the stick tang has more mass to absorb stress.

This is the type of stick tang that is useless for absorbing shock.  Many of the Scandi-blade knives from Northern Europe have this type of tang.  Remember, however, that most woodsmen in those regions are working with softer hardwoods and they invariably bring along an axe for the tougher chopping jobs.  The knife, for them, is a woodworking tool and nothing else.  People in other regions of the globe have erroneously believed these Scandinavian knives can be used for working on hardwoods like mesquite, ebony, brasil etc..

This is a small “Woods Roamer” design incorporating a true full tang.  The mass is increased at the tip to give the overall blade added structural integrity for batoning ultra-dense woods like mesquite and guayacan.  It incorporates a true full tang with only three 1/8 inch pin holes.  The knife features a lazy-S pattern that aids in reducing hand, wrist and elbow fatigue.

This is the knife drawn above brought to fruition.  Made from quarter inch thick leaf-spring 5160 steel the knife was designed around the parameters noted at the top of this post.

KNIFE NUMBER ONE
Blade length 7 inches
Handle Length 4 ½ inches
KNIFE NUMBER TWO
Blade Length 7 3/8 inches
Handle Length 4 ½ inches





Both knives were differentially tempered with the hardest along the bevel edge, softer along the spine and softest at the main stress area at the juncture of blade and handle.

A woodsman’s knife in desert and brushland regions is quite different from what many are used to seeing in northern forested areas.  To begin with the need to make feather sticks—which seems to be paramount in the northern climes—is of little consequence in the desert and brushlands.  Deserts and brushlands are dry climates where one seldom encounters wet wood.  Even when it does rain, the experienced woodsman knows what hardwood shrubs to gather that are filled with flammable oils that catch easily when struck with a spark or flame.  Furthermore, brushland and desert regions are known for exceedingly hard woods.  The often pictured “bushcraft knife” with its short four-inch blade and Scandi-grind is more often than not useless when encountering ultra-dense woods covered with two or three inch thorns.  Cute little knives might be just the ticket for Swedes and their neighbors (They sure do live in beautiful country!) but they are too anemic for places where wood grows hard and dries into rock and where everything you encounter is going to prick, stick and otherwise jab you.


One of the knives pictured has a hole; a vestigial leaf-spring connection that I find useful in making arrows as it’s perfect for sizing and straightening.  One more note: While other steels are quite useful I selected 5160 because of its robust qualities especially when used against South Texas hardwoods.

6 comments:

  1. Very well written and thoughtful as always. Most people when thinking of the full-tang vs otherwise have little or no knowledge of the physics of how and when something breaks. Thank you for your constant reality checks.

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    1. Thank you for your comment. You, sir, sound like someone who understands knives.

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  2. I don't have as much field experience as you by any means and it has been years since I have built a knife. However, since those days, I have always had an interest in learning about the history, origins, and use of bladed tools of all sorts from various places around the world. You might say I am more academic in that way. I don't have the space nor facilities to build tools now but it is something I would like to move toward having. Best.

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    1. Bladed tool, whether from rocks, copper, brass, iron, bone or glass, have played such an intrinsic part of the story of humankind that it is only natural that we are fascinated by them. I hope you journey continues.

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  3. rather impressed with the technical breakdown. too few understand the physics behind knife design.

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    1. Thanks for the comment. When I was a kid I memorized ballistic tables and learned all the algorithms associated with sectional densities and ballistic coefficients. I guess it was just a matter of transferring that curiosity into metallurgy and knife design.

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